Image forming apparatus, parameter adjustment method, and control program

Abstract

To maintain desired glossiness.SOLUTION: An image forming apparatus includes a fixing part 136 for fix and fixing a toner image on a sheet, a glossiness setting part 111 for setting a target glossiness, and a parameter adjustment part 112 for adjusting at least one parameter of a fixing target temperature and a conveyance condition of the sheet in the fixing part by using a glossiness control temperature Tgc so as to obtain the set target glossiness.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an image forming apparatus, a parameter adjustment method, and a control program. [Background technology]

[0002] There is a demand for fixing devices that can stably fix high-quality images onto paper. In addition to high quality, recent fixing devices are also required to achieve a wider range of gloss levels, from low gloss levels suitable for plain paper to high gloss levels suitable for photographic images. Generally, in electrophotographic image forming devices, paper on which a toner image has been formed in the image forming unit is passed through a fixing nip formed by fixing members such as rollers. The toner image is then fixed to the paper by applying heat and pressure.

[0003] It is known that the glossiness of an image formed in an image forming apparatus generally varies depending on the combination of multiple parameters, such as fixing temperature, conveyance speed, and nip width. For example, the apparatus disclosed in Patent Document 1 is equipped with a fixing mechanism and a gloss sensor, and the fixing mechanism temperature is changed in multiple stages while measuring the glossiness at each stage, thereby obtaining a gloss-versus-temperature curve that indicates the relationship between glossiness and fixing mechanism temperature. Then, in response to a user's instruction of a desired gloss level, the fixing mechanism temperature is set using the gloss-versus-temperature curve. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 5557613 Summary of the Invention [Problem to be solved by the invention]

[0005] On the other hand, parameters such as fixing temperature, conveyance speed, and nip width may be adjusted for purposes other than adjusting glossiness. For example, adjustments may be made by a user, such as an operator or service technician, to change image quality other than glossiness, or by the control unit automatically adjusting the parameters due to other factors. In such cases, adjustments to these parameters may result in unintended changes in glossiness. Alternatively, glossiness may change due to factors such as the time elapsed since the image forming apparatus was turned on or the temperature saturation of the fixing unit caused by continuous printing.

[0006] In such a case, the user is required to perform the work of adjusting the glossiness again, and there is a problem in that the adjustment process results in unnecessary paper consumption.

[0007] The present invention has been made in view of the above circumstances, and has an object to provide an image forming apparatus and a parameter adjustment method that can maintain a desired glossiness. [Means for solving the problem]

[0008] The above object of the present invention can be achieved by the following means.

[0009] (1) a fixing unit that fixes a toner image on a sheet of paper; a gloss setting unit that sets a target gloss; a parameter adjusting unit that adjusts at least one parameter of a fixing target temperature and a paper transport condition in the fixing unit using the gloss control temperature so as to achieve the set target gloss; An image forming apparatus comprising:

[0010] (2) The image forming apparatus according to (1), wherein the parameter adjustment unit adjusts the parameter in accordance with the difference between the detected fixing temperature of the fixing member of the fixing unit and the gloss control temperature.

[0011] (3) The image forming apparatus according to (1), wherein the parameter adjustment unit adjusts the parameter according to the difference between the target fixing temperature that controls the temperature of the fixing member of the fixing unit and the gloss control temperature.

[0012] (4) The image forming apparatus according to (1) above, wherein the transport conditions include parameters of a paper transport speed and a nip width in the fixing unit.

[0013] (5) The image forming apparatus according to (1), wherein the gloss control temperature is set in advance for each paper type.

[0014] (6) A glossiness estimation model showing the relationship between glossiness and a glossiness control constant is provided, the adjustment of the parameters is performed using the glossiness estimation model; The image forming apparatus according to (1) above, wherein the gloss control constant is defined by the following formula: X=W / V×(T-Tgc) (In the formula, X is the gloss control constant, T is the target fixing temperature, V is the conveying speed, W is the nip width, and Tgc is the gloss control temperature.) (7) The image forming apparatus according to (6), wherein the gloss estimation model is a sigmoid function.

[0015] (8) The image forming apparatus according to (6), wherein the gloss level estimation model is set for each paper type.

[0016] (9) A parameter adjustment method for an image forming apparatus having a fixing unit that fixes a toner image on a sheet, comprising: Step (a) of setting a target gloss level; and (b) adjusting at least one parameter of the fixing target temperature and the paper transport conditions in the fixing section using the gloss control temperature so as to achieve the target gloss level set in step (a).

[0017] (10) The parameter adjustment method according to (9) above, wherein in the step (b), the parameter is adjusted according to a difference between the detected fixing temperature of the fixing member of the fixing unit and the gloss control temperature.

[0018] (11) The parameter adjustment method according to (9) above, wherein the gloss control temperature is set for each paper type.

[0019] (12) A glossiness estimation model showing the relationship between glossiness and a glossiness control constant is provided, The step (b) is performed using the gloss estimation model, The parameter adjusting method according to (9) above, wherein the glossiness control constant is defined by the following formula: X=W / V×(T-Tgc) (In the formula, X is the gloss control constant, T is the target fixing temperature, V is the conveying speed, W is the nip width, and Tgc is the gloss control temperature.) (13) A control program for causing a computer to execute the parameter adjustment method according to any one of (9) to (12) above. [Effects of the Invention]

[0020] The image forming apparatus according to the present invention includes a fixing unit that fixes a toner image on a sheet, a gloss setting unit that sets a target gloss level, and a parameter adjustment unit that adjusts at least one of a target fixing temperature and a sheet transport condition in the fixing unit using a gloss control temperature so as to achieve the set target gloss level, thereby maintaining the gloss level of the sheet at a desired level. [Brief explanation of the drawings]

[0021] Advantages and features provided by one or more embodiments of the present invention will be more fully understood from the following detailed description and the accompanying drawings, which are for purposes of illustration only and are not intended to be limiting. [Figure 1] 1 is a diagram illustrating a schematic configuration of an image forming apparatus according to an embodiment of the present invention. [Figure 2]FIG. 1 is a block diagram showing a configuration of an image forming apparatus. [Figure 3A] 1 is an example of a gloss vs. nip width graph. [Figure 3B] 10 is an example of a graph showing gloss level versus conveyance speed. [Figure 3C] 1 is an example of a graph showing glossiness versus fixing temperature. [Figure 4A] 10 is an example of a glossiness-composite parameter graph for paper type A. [Figure 4B] 10 is an example of a glossiness-composite parameter graph in which gloss control temperature is applied to the composite parameter for paper type A. [Figure 5A] 10 is an example of a glossiness-composite parameter graph for paper type B. [Figure 5B] 10 is an example of a glossiness-composite parameter graph in which gloss control temperature is applied to the composite parameter for paper type B. [Figure 6A] 10 is an example of a glossiness-composite parameter graph for paper type C. [Figure 6B] 10 is an example of a glossiness-composite parameter graph in which gloss control temperature is applied to the composite parameter for paper type C. [Figure 7] 10 is an example of a glossiness estimation model to which a linear function is applied. [Figure 8A] 10 is an example of a gloss estimation model to which a sigmoid function is applied for paper type A. [Figure 8B] 10 is an example of a gloss estimation model to which a sigmoid function is applied for paper type B. [Figure 8C] 10 is an example of a gloss estimation model to which a sigmoid function is applied for paper type C. [Figure 9] 10 is a flowchart showing a parameter adjustment process. [Figure 10] 10 is a subroutine flowchart showing the calculation process of the gloss control constant in step S02 of FIG. 9. [Figure 11A] 10 is an example of a setting screen for a gloss target value. [Figure 11B] FIG. 10 is a diagram showing a procedure for setting a target gloss value from a gloss control constant. [Figure 12]10 is a subroutine flowchart showing the target gloss level setting process in step S02 of FIG. 9 in another example. [Figure 13] 10 is a subroutine flowchart showing the process of setting the target gloss level in step S02 of FIG. 9 in another example. [Figure 14] FIG. 10 is a diagram showing a procedure for setting a glossiness control constant from a glossiness target value. [Figure 15] 10 is a flowchart showing the parameter adjustment process in step S08 of FIG. 9. [Figure 16] 10 is a flowchart showing the parameter adjustment process in step S08 of FIG. 9. [Figure 17] 10 is a flowchart showing the process performed when the paper type is changed in one print job in Modification 1. [Figure 18] 10 is a flowchart showing a process performed when a parameter is adjusted by a user in Modification 2. DETAILED DESCRIPTION OF THE INVENTION

[0022] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. In the description of the drawings, identical elements are designated by the same reference numerals, and redundant description will be omitted. The dimensional proportions in the drawings are exaggerated for the sake of explanation and may differ from the actual proportions. In this embodiment, paper includes paper made from plant-derived mechanical pulp and / or chemical pulp. Furthermore, paper types (paper types) include coated gloss paper and matte paper, and uncoated plain paper and fine paper.

[0023] Fig. 1 is a diagram showing a schematic configuration of an image forming apparatus 1000 according to this embodiment. As shown in Fig. 1, the image forming apparatus 1000 includes an image forming apparatus main body 10 and a paper feed unit 20, which are mechanically and electrically connected to each other for communication.

[0024] (Image forming apparatus main body 10) The image forming apparatus main body 10 includes a control unit 11, a storage unit 12, an image forming unit 13, a paper feed conveyance unit 14, an operation panel 15, a fixing shaft distance adjustment mechanism 16, a communication unit 17, a paper detection device 18, etc. These are connected to each other via signal lines such as a bus for exchanging signals.

[0025] (Control unit 11) The control unit 11 is composed of a CPU, a ROM, a RAM, etc. The control unit 11 executes various processes by executing programs stored in the ROM or in the storage unit 12 (described later), and controls each unit of the device and performs various arithmetic processes in accordance with the programs. The control unit 11 functions as a gloss setting unit 111 and a parameter adjustment unit 112.

[0026] (Glossiness setting unit 111) The gloss level setting unit 111 sets the target gloss level. The target gloss level can be set as follows. (1a) Receipt of a desired relative gloss value by the user through the operation panel 15. (2a) The user accepts the absolute value of the desired glossiness through the operation panel 15. (3a) When forming images for one print job, the initial glossiness is set as the target glossiness so that the glossiness is constant within the print job. In this case, the initial glossiness is estimated at the beginning of the print job (for example, one to several sheets), and this glossiness is set as the target glossiness. In the case of (3), the target glossiness is maintained to suppress fluctuations in glossiness within the same print job due to the elapsed time since the image forming apparatus main body was turned on or temperature saturation of the fixing unit due to continuous printing. The target glossiness set by the glossiness setting unit 111 is stored in the memory unit 12.

[0027] (Parameter adjustment unit 112) Through the process described below (e.g., FIG. 9 ), the parameter adjustment unit 112 adjusts image formation parameters so that the gloss level becomes the target gloss level. The parameter adjustment uses the difference (T-Tgc) between the fixing temperature and the gloss control temperature (see, e.g., Equations (1), (5), and (6) described below). The parameters include the target fixing temperature (the target value of the fixing control temperature, also referred to as the target fixing temperature Tt) and / or the conveying conditions. The conveying conditions also include the paper conveying speed and the fixing nip width (hereinafter simply referred to as the nip width). Priorities may be set in advance for selecting the parameters to be adjusted, and three parameters may be selected according to the priorities. For example, the target fixing temperature, the nip width, and the conveying speed may be prioritized in this order. Each parameter has an adjustment range, and when the upper or lower limit of the adjustment range is reached, the next parameter is selected. For example, when increasing the gloss level, the target fixing temperature is selected first. When the target fixing temperature reaches the upper limit of the adjustment range, the nip width is selected and adjusted to widen it. Furthermore, if the nip width also reaches the upper limit of the adjustment range, the next transport speed is selected and adjusted to decrease this transport speed. Note that when adjusting parameters during printing, a process may be performed to put the print on hold until the parameters are changed. For example, this waiting process may include temporarily suspending the transport drive or widening the paper gap without stopping the transport drive.

[0028] (Storage unit 12) The storage unit 12 comprises auxiliary storage units such as a ROM for storing various programs and data in advance, a RAM for temporarily storing programs and data as a working area, and a hard disk for storing various programs and data.

[0029] The storage unit 12 also stores information about the paper stored in each paper feed tray. The paper information includes information about the paper brand, size (paper width, paper length), basis weight (basis weight), and paper type (coated paper, plain paper, high-quality paper, rough paper, etc.), which is set by a paper type determination process described below. The storage unit 12 may also store a trained model used to determine the paper brand or paper type, and a paper profile (both described below).

[0030] The memory unit 12 also stores a gloss estimation model, a gloss control temperature (Tgc), and a target gloss. The gloss estimation model and gloss control temperature are set for each paper type and are stored in association with the paper type. The target gloss is stored in association with either the paper type, the print job, or the entire device.

[0031] The glossiness estimation model is a function that describes the relationship between the glossiness control constant x and the glossiness. A polynomial function or a sigmoid function can be applied as the function. The glossiness control temperature (Tgc) is a factor of the glossiness control constant x. The target glossiness that can be stored includes a target glossiness that is commonly applied to the image forming apparatus 1000, a target glossiness for each paper type, and a target glossiness for each print job. The glossiness estimation model and the glossiness control temperature will be described in detail later.

[0032] (Image forming unit 13) Image forming unit 13 forms an image, for example, by electrophotography. As shown in FIG. 1, image forming unit 13 includes writing units 131 corresponding to the respective basic colors of Y (yellow), M (magenta), C (cyan), and K (black), photosensitive drums 132, and developing units 133 containing two-component developers each composed of toner and carrier for each color. Image forming unit 13 also includes an intermediate transfer belt 134, a secondary transfer unit 135, and a fixing unit 136. Toner images formed on photosensitive drums 132 by developing units 133 for each color are superimposed on intermediate transfer belt 134 and transferred to paper 90 conveyed by secondary transfer unit 135. The toner images on paper 90 are fixed to paper 90 by heating and pressing in fixing unit 136 downstream.

[0033] The image forming unit 13 also includes a fixing unit 136 .

[0034] The fixing unit 136 includes a heating roller 31 and a pressure roller 32 as fixing members, and applies pressure and heat to the paper 90 conveyed to the fixing nip between the two rollers, thereby melting and fixing the toner image on the paper 90 to its surface.

[0035] The heating roller 31 comprises, from the inside out, a cylindrical metal core, an elastic layer made of a material such as silicone rubber or foamed silicone rubber formed on the surface of the core, and a release layer made of a material such as fluororesin. Multiple halogen lamp heaters are arranged inside the core. The length of the heating roller 31 in the direction of its rotation axis (hereinafter simply referred to as the "width direction"), which is perpendicular to the conveyance direction of the paper 90, is long enough to fix paper 90 of the maximum paper width that can be conveyed. The multiple heaters 2 may be composed of heaters with different heat distributions (light distribution characteristics) corresponding to the multiple paper widths that can be fed by the device.

[0036] The pressure roller 32 comprises, from the inside out, a cylindrical metal core, an elastic layer made of a material such as silicone rubber or foamed silicone rubber formed on the surface of the core, and a release layer made of a fluororesin or the like. The outer diameter and axial length of the pressure roller 32 are approximately the same as those of the heating roller 31. A heater may also be arranged inside the core of the pressure roller 32.

[0037] The temperature sensor 33 detects the temperature of the surface of the heating roller 31. Multiple temperature sensors 33 may be arranged. For example, they are arranged at different positions in the width direction, such as the center, the rear side, and the front side, to measure the temperature distribution in the width direction of the heating roller 31. As the temperature sensor 33, for example, a thermistor arranged in a non-contact state with the heating roller 31 is used.

[0038] (Paper feed conveyance section 14) The paper feed conveyance unit 14 includes a plurality of paper feed trays 141, 142, conveyance paths 143, 144, etc. The conveyance paths 143, 144 include a plurality of conveyance roller pairs provided along these conveyance paths, and a drive motor (not shown) that drives these conveyance roller pairs. The paper feed conveyance unit 14 includes a feed roller that feeds the topmost sheet of paper 90 stacked in the paper feed trays 141, 142, and sends the sheets 90 in the paper feed trays one by one to the downstream conveyance path. A paper detection device 18 is arranged upstream of the registration rollers (the roller pair immediately upstream of the secondary transfer unit 135) on the conveyance path 143.

[0039] The paper feed conveyance unit 14 conveys paper 90 fed from a paper feed tray 141 or the like. After an image is formed on the paper 90 conveyed along the conveyance path 143 by the image forming unit 13, the paper is discharged onto a paper output tray 145. When performing double-sided printing, in which an image is also formed on the back side of the paper 90, the paper feed conveyance unit 14 conveys the paper 90 with an image formed on one side to a conveyance path 144 for double-sided image formation located at the bottom of the device main body. The paper 90 conveyed to this conveyance path 144 is turned over on a switchback path, and then merges with the conveyance path 143 for single side printing, where an image is again formed on the other side of the paper 90 by the image forming unit 13.

[0040] (Operation panel 15) Operation panel 15 is equipped with a touch screen, numeric keypad, start button, stop button, etc. Operation panel 15 displays the status of image forming apparatus main body 10 or image forming apparatus 1000, roller life information (replacement timing), etc., and is used by the user to set the type of paper placed in paper feed tray 141, etc., and to input instructions. In addition, operation panel 15 allows the user to set the desired gloss level (see FIG. 11A, described below).

[0041] (Fixing axis distance adjustment mechanism 16) The fixing shaft distance adjustment mechanism 16 moves the shaft of one of the two fixing members to adjust the nip width. For example, the fixing shaft distance adjustment mechanism 16 supports both sides of the rotation shaft of the pressure roller 32. The fixing shaft distance adjustment mechanism 16 changes the distance between the axes of the two fixing members by moving the rotation shaft of the pressure roller 32 up and down toward the axis of the opposing heating roller 31. The fixing shaft distance adjustment mechanism 16 is composed of a cam mechanism and a drive source such as a motor. The control unit 11 has a control table that describes the correspondence between the drive amount of the fixing shaft distance adjustment mechanism 16, the shaft height of the pressure roller 32, and the nip width, and controls the drive amount of the fixing shaft distance adjustment mechanism 16 so that the set nip width is achieved.

[0042] (Communications Department 17) The communication unit 17 is an interface for communicating with an external device via a network. It is a circuit.

[0043] (Paper detection device 18) The paper detection device 18 has a plurality of sensors 1 to n, and detects the physical property values ​​of the paper 90 transported on the transport path 143. The sensors include sensors that detect paper thickness, basis weight, moisture content, stiffness, surface properties, and paper resistance (electrical resistance).

[0044] "Paper thickness" is obtained by detecting characteristics corresponding to the thickness of the paper using sensor 1. Sensor 1 sandwiches the paper between two members and measures the distance between the two members.

[0045] The "basis weight" is obtained by using sensor 2 to detect characteristics corresponding to the basis weight of the paper. Sensor 2 is composed of, for example, a transmissive or reflective optical sensor. The basis weight is obtained by using sensor 2 to measure the attenuation (transmittance) of light passing through the paper.

[0046] The "moisture content" is obtained by detecting characteristics corresponding to the moisture content (also called water content) of the paper using sensor 3. For example, sensor 3 optically detects the amount of light absorbed by OH groups using a near-infrared method using light transmitted through the paper.

[0047] "Stiffness" is obtained by detecting characteristics corresponding to the stiffness of the paper using sensor 4. Sensor 4 measures the pressing force when pressing the rear end of the free end of the paper. "Stiffness" constitutes a value related to the bending strength of the paper.

[0048] "Surface texture" is obtained by using sensor 5 to detect characteristics corresponding to the smoothness of the paper surface. "Surface texture" is also called smoothness. Sensor 5 is composed of an irradiating unit and a light receiving unit. Sensor 5 irradiates the paper surface with light at an incident angle of, for example, 75 degrees, and optically detects the specularly reflected light and diffusely reflected light from the paper surface using the two sensors. "Surface texture" constitutes a value related to the paper surface condition.

[0049] "Paper resistance" is obtained by detecting characteristics corresponding to the electrical resistance inside or on the surface of the paper using sensor 6. Sensor 6 measures the voltage and current that flows when a high voltage is applied to the paper. "Paper resistance" constitutes a value related to the volume resistance of the paper.

[0050] (Paper type or brand determination process) The paper type or brand of paper 90 stored in the paper feed tray is set by the user via operation panel 15. Alternatively, paper detection device 18 detects stored paper 90 as follows, and determines the paper type or brand based on the detection data.

[0051] (Paper type determination process) A sheet of paper 90 is conveyed from the target paper feed tray, and its physical properties (also referred to as paper characteristics) are measured by the paper detection device 18. The paper physical properties measured include those measured by the sensors described above. For example, the control unit 11 determines the paper type and measures the basis weight classification based on the multiple paper physical properties obtained, such as basis weight, paper thickness, and surface properties. This determination may be rule-based, and the paper type and basis weight classification are determined using a trained model (paper type discrimination engine) and a paper profile. Here, a "paper profile" is a pre-registered profile for a particular sheet of paper, which is associated with the measured values ​​of the paper detection device 18, characteristic data input by the user, paper size, and an arbitrary identification name (e.g., paper brand). The paper brand is a more specific classification of paper types that identifies the brand of the paper manufacturer. When the paper brand is identified, the paper type is also identified. The "paper type discrimination engine," also referred to as a trained model, is a trained model generated through supervised learning using training data, with the detection output of the paper detection device 18 for the paper 90 as an input value and the paper type information for the paper 90 set by the user as a correct label. After the control unit 11 determines the paper type and basis weight classification, the determination result is displayed on the operation panel 15. The user confirms the determination result (by pressing the confirm button), and the paper feed tray and paper type information are associated and stored in the memory unit 12. Furthermore, in the paper type determination process, if there is no paper type (paper brand) with the same paper physical properties, the paper profile in the memory unit 12 is used to determine whether there is data with nearby paper physical properties. The parameter adjustment unit 112 derives the gloss control temperature Tgc and glossiness estimation model for the target paper using the gloss control temperature Tgc and glossiness estimation model associated with one or more paper types (paper brands) with nearby paper physical properties. For example, if there are two gloss control temperatures Tgc and gloss estimation models with similar paper properties, the gloss control temperature Tgc and gloss estimation model for the target paper can be derived by interpolation or extrapolation depending on the Euclidean distance between the two paper properties.

[0052] (Paper feed unit 20) As shown in FIG. 1, paper feed unit 20 includes paper feed conveyance section 24. In addition to paper feed conveyance section 24, paper feed unit 20 also includes a control section, a storage section, and a communication section (none of which are shown) that communicates with image forming apparatus main body 10, and these are connected to each other via signal lines such as a bus for exchanging signals. Paper feed conveyance section 24 includes multiple paper feed trays 241, 242, and 243, and a conveyance path 244. Paper 90 conveyed from each paper feed tray is transported downstream to image forming apparatus main body 10, where paper characteristics are measured by paper detection device 18 and an image is formed in image forming section 13.

[0053] (Gloss estimation model, gloss control temperature) Next, the gloss estimation model and the gloss control temperature Tgc will be described with reference to FIGS. 3A to 8C. Here, gloss is expressed as glossiness. In this embodiment, 60-degree specular glossiness is used as the glossiness according to the method defined in the JIS standard (JIS Z8741). The glossiness is a value that defines a glossiness of 100% as a reflectance of 10% at an incident angle of 60 degrees on a glass surface with a refractive index of 1.567. The glossiness was measured using a GM-60A glossmeter manufactured by Konica Minolta, Inc.

[0054] The gloss on the paper is controlled by the fixing temperature, nip width, and nip time. Here, the fixing temperature refers to the temperature actually measured (by temperature sensor 33) on the surface of heating roller 31 when fixing paper. A related term is the target fixing temperature. The target fixing temperature refers to the controlled temperature of heating roller 31. Control unit 11 controls the power supply to the heater that heats fixing unit 136 so that the actual measurement value of temperature sensor 33 becomes the target fixing temperature. As described above, nip width refers to the length in the conveyance direction of the nip formed between heating roller 31 and pressure roller 32. The nip width is variably adjusted by fixing shaft distance adjustment mechanism 16.

[0055] Nip time is the time it takes for a sheet of paper to pass through the nip. Under conditions where the nip width is constant, nip time is inversely proportional to the sheet conveying speed. The conveying speed is also called the system speed and is a speed commonly applied to the entire image forming apparatus main body 10. The conveying speed is variable by controlling the rotation speed of the drive motor (not shown). Note that the conveying speed may be changed by changing only the conveying speed of the fixing unit 136. If the speed difference between the system speed and the conveying speed of the fixing unit 136 is within a predetermined range (for example, within a few percent), the speed difference can be absorbed by the slack in the sheet of paper.

[0056] 3A to 3C are scatter diagram graphs showing the influence of control factors (hereinafter referred to as parameters) of nip width, conveyance speed, and fixing temperature on glossiness for a specific paper type A. However, as shown in Figs. 3A to 3C, the relationship between glossiness and each individual parameter is not apparent.

[0057] Therefore, it is assumed that glossiness is correlated with the amount of heat applied to the toner, and the following assumptions are made to synthesize parameters. (1b) The wider the nip width (due to the increased heating time), the higher the glossiness. In other words, it is proportional to the nip width. (2b) The slower the conveying speed (the longer the fixing time), the higher the glossiness. In other words, it is inversely proportional to the conveying speed. (3b) The higher the fixing temperature, the higher the glossiness. (4b) However, although it is affected by the fixing temperature, it is not simply proportional; a fixing temperature exceeding a certain temperature (hereinafter referred to as the gloss control temperature or gloss control temperature Tgc) is proportional to the gloss level.

[0058] 4A and 4B are example scatter plots of glossiness versus composite parameters for paper type A. In FIG. 4A, parameters are composited based on the assumptions (1b) to (3b) above, while in FIG. 4B, parameters are further composited by adding (4b). That is, in FIG. 4A, the horizontal axis is nip width / speed * fixing temperature, and in FIG. 4B, it is nip width / speed * (fixing temperature - gloss control temperature) (the * character indicates multiplication; the same applies below). Note that in the graphs such as FIG. 4A and FIG. 4B, and in the following description, nip width may be represented as W, conveying speed as V, and fixing temperature as T. In the following, the composite parameters (nip width / speed * (fixing temperature - gloss control temperature)) from (1b) to (4b) are referred to specifically as the "gloss control constant" or "gloss control constant x0." That is, they are defined by the following equation (1):

[0059]

number

[0060] Here, W is the nip width, V is the conveying speed, T is the fixing temperature (or the target fixing temperature), and Tgc is the gloss control temperature.

[0061] The gloss control constant xc and gloss control temperature Tgc are calculated using an optimization method, for example, to calculate the gloss control constant xc and gloss control temperature Tgc that have the highest correlation with the gloss level estimation model (described later), i.e., that minimize the sum of the difference values ​​between the plots.

[0062] In FIG. 4A, the relationship between the synthesis parameters and the glossiness is weak, but in FIG. 4B, the relationship between the synthesis parameters and the glossiness can be seen.

[0063] Similar trends are observed for paper types B and C other than paper type A. Figures 5A and 6A are scatter plot graphs showing the relationship between composite parameters (1b) to (3b) and glossiness for paper type B and paper type C, respectively. Figures 5B and 6B are scatter plot graphs showing the relationship between composite parameters (1b) to (4b) and glossiness for paper type B and paper type C, respectively.

[0064] (Glossiness estimation model) The gloss level estimation model will be described below with reference to Figures 7 to 8C. Each plot in Figures 7 to 8C corresponds to one of Figures 4B, 5B, and 6C.

[0065] FIG. 7 shows the application of a linear function as a glossiness estimation model.

[0066]

number

[0067] The linear function shown in FIG. 7 is obtained by calculating data a0 to an from the polynomial model of the above equation (2) using a mathematical optimization method.

[0068] 8A to 8C show the application of a sigmoid function as a gloss estimation model. The sigmoid function is applied, and the model formula is created by adding scaling a in the x-axis direction, x-axis offset x0, scaling b in the y-axis direction, and y-axis offset y0. The gloss K is calculated from the gloss control constant x using the formula K=f(x) as shown in the following formula (3).

[0069]

number

[0070] a, b, x0, y0 are calculated from the data using mathematical optimization. Using the sigmoid function in this way shows that there is a higher correlation with the model.

[0071] Next, we will explain the inverse function used in the processing described later. When gloss level K is given, the inverse model g(K) for finding the gloss control constant x is obtained by transforming the format y=f(x) so that x is a function of y, as shown in the following equation (4).

[0072]

number

[0073] (parameter adjustment process) The parameter adjustment process executed in the image forming apparatus will be described below with reference to Figures 9 to 16. Figure 9 is a flowchart showing the parameter adjustment process.

[0074] (Step S01) When the control unit 11 receives the print job and starts printing (YES), the process proceeds to step S02.

[0075] (Step S02) The control unit 11 reads out the target glossiness from the storage unit 12. There are three types of processing as examples of setting the target glossiness to be read out here. These will be explained in order below. (1a) Acceptance of target gloss relative value setting from the user. (2a) Acceptance of absolute value setting of target glossiness from the user. (3a) When forming an image for one print job, the initial glossiness is set as the target glossiness so that the glossiness is constant within the print job.

[0076] <(1a) Setting the relative value of the target gloss level by the user> Fig. 10 is a subroutine flowchart showing the target gloss level setting process in step S02. The process in Fig. 10 (as well as Fig. 12 described later) may be set at a timing independent of the start of printing, or may be set immediately before the start of printing.

[0077] (Step S11) A target gloss level setting is accepted from the user via the operation panel 15 or the like. Fig. 11A shows an example of a target gloss level setting screen 151 displayed on the operation panel 15. Note that this setting screen may also be set using a print setting application on a terminal device such as a personal computer operated by the user.

[0078] On the setting screen 151, the user can operate the buttons in area a1 to relatively increase or decrease the gloss level. The user can set the target gloss level in five steps, from +2 to -2. As shown in FIG. 11A , the current estimated gloss level may be displayed in area a3 for reference. By selecting "Increase Gloss +2," "Increase Gloss +1," "Reset +0," "Decrease Gloss -1," or "Decrease Gloss -2," the user can change the current gloss level to +10, +5, +0, -5, or -10, respectively. The user can also select the application scope from "Paper Type," "Print Job," or "Common to Device" by enabling one of the radio buttons in area a2. The default is per paper type. The target paper type is selected on a separate screen. In FIG. 11A , paper type A for tray 1 is selected as the target. The application scope is also selected as per paper type. The gloss level is set to "Increase Gloss +1" (target gloss level +5).

[0079] (Step S12) Here, the control unit 11 acquires the paper type information. The paper type information is registered in the storage unit 12 in association with the paper feed tray used in the print job.

[0080] (Step S13) The gloss setting unit 111 estimates the current gloss level. To estimate the gloss level, the gloss setting unit 111 acquires a gloss level estimation model f(x) for each paper type from the storage unit 12. The gloss setting unit 111 then calculates the gloss level control constant xc (xc:W / V*(T-Tgc)) of the composite parameters (1b to 4b) from the current parameters (fixing temperature T, conveying speed V, nip width W) and substitutes this into the gloss level estimation model to obtain the gloss level. FIG. 11B is a diagram corresponding to FIG. 8A. If the gloss level control constant xc is "8", a gloss level of 50 can be obtained by substituting this into the gloss level estimation model f(x).

[0081] (Steps S14 and S15) The gloss setting unit adds the target setting (+5) set in step S11 to the estimated gloss. That is, +5 is added to the gloss of 50 obtained in step S13 to obtain 55. The gloss after the addition is then set as the target gloss (=55), linked to the applicable paper type, and stored in the memory unit 12. This ends the processing in FIG. 10, and the process returns to the processing from step S03 onwards in FIG. 9 (RETURN).

[0082] <(2a) Setting the absolute value of the target gloss level by the user> FIG. 12 is a subroutine flowchart showing the target gloss level setting process in step S02 in another example, which corresponds to (2a) above.

[0083] (Steps S21 and S22) The gloss setting unit 111 accepts the setting of the target gloss (absolute value) from the user. For example, the target gloss may be input via a setting screen similar to the setting screen 151 of FIG. 11A. The applicable range of the target gloss may also be similarly selectable. The gloss setting unit 111 stores the accepted gloss target value in the memory unit. This completes the processing of FIG. 12, and the processing returns to step S03 and subsequent steps of FIG. 9 (return).

[0084] <(3a) Setting the gloss level at the beginning of the print job as the target gloss level> Figure 13 is a subroutine flowchart showing the target gloss level setting process in step S02 in another example, which corresponds to (3a) above. In the example shown in Figure 13, parameters are adjusted so that the initial gloss level is maintained during the execution of one print job. As shown below, the initial gloss level of the print job is set as the target gloss level during this print job.

[0085] (Step S31) The control unit 11 causes the image forming unit 13 to form an image on the first sheet of paper 90 of the print job. The glossiness (estimated value) at the time of image formation on this first sheet of paper 90 is set as the glossiness target by the following process.

[0086] (Step S32) Here, the control unit 11 acquires paper type information for the print job to be executed. The paper type information is registered in association with the paper feed tray.

[0087] (Step S33) The gloss setting unit 111 estimates the initial gloss of a print job. For example, it estimates the gloss of the first sheet. The gloss setting unit 111 acquires a gloss estimation model (f(x)) for each paper type from the memory unit 12, and then calculates a gloss control constant xc (W / V*(T-Tgc)) from the current parameters (fixing temperature T, conveying speed V, nip width W). The gloss is obtained by substituting this into the gloss estimation model.

[0088] (Step S34) The gloss level setting unit 111 associates the obtained estimated gloss level with the applicable paper type as the target gloss level and stores it in the storage unit 12. This ends the processing in FIG. 13, and the process returns to the processing from step S03 onward in FIG. 9 (RETURN).

[0089] (Step S03) As shown in Fig. 9, the control unit 11 acquires paper type information for the paper 90 to be used in printing. The information on the paper type to be used in printing is set in the print job. The paper type information is set in association with the paper feed tray to be used in the print job. Note that in the examples of Figs. 10 and 13, the paper type information has already been acquired, so in that case the processing here may be omitted.

[0090] (Step S04) (Steps S04 to S06) In steps S04 to S06, the parameter adjustment unit 112 determines a glossiness control constant (xc) based on the acquired target glossiness (=55). The parameter adjustment unit 112 acquires a glossiness estimation model corresponding to the paper type and a glossiness control temperature Tgc from the storage unit 12. The parameter adjustment unit 112 substitutes the target glossiness acquired in step S02 into the inverse function g(Z) of the glossiness estimation model acquired from the storage unit to determine the glossiness control constant xc. An example of the inverse function is shown in equation (3) above. Figure 14 is a diagram corresponding to Figure 11B. For example, if the target glossiness is "55" (current glossiness 50 + correction 5) according to the processing of Figure 10, substituting this into the inverse function g(Z) of the glossiness estimation model reveals that the glossiness control constant xc is "9".

[0091] (Step S07) The parameter adjustment unit 112 acquires the current parameters, which are the fixing temperature T0, the conveying speed V0, and the nip width W0.

[0092] (Step S08) The parameter adjustment unit 112 adjusts parameters to maintain gloss. The parameters adjusted here are at least one of the target fixing temperature, the conveying speed, and the nip width. In the following, an example of adjusting the target fixing temperature will be described first as a representative example, and then an example of adjusting the nip width will be described. Although a description of the conveying speed will be omitted, the conveying speed can also be adjusted in the same way.

[0093] (Adjustment of fixing target temperature T1) FIG. 15 is a subroutine flowchart showing the parameter adjustment process in step S08.

[0094] (Step S510) The parameter adjusting unit 112 calculates the corrected fixing target temperature T1 that becomes the gloss control constant xc determined in step S06. The calculation is performed using the following equation (5), which is a modification of the above equation (1).

[0095]

number

[0096] (Step S520) Thereafter, the parameter adjusting unit 112 changes the target fixing temperature from T0 to T1 to control the temperature of the fixing unit 136 during image formation. Then, the process of FIG. 15 ends, and the process returns to FIG. 9, where the processes from step S09 onwards are performed (return).

[0097] (Adjusting the nip width W1) FIG. 16 is a subroutine flowchart showing the parameter adjustment process in step S08.

[0098] (Step S610) The parameter adjustment unit 112 calculates the corrected nip width W1 that becomes the gloss control constant xc determined in step S06. The calculation is performed using the following equation (6), which is a modification of the above equation (1).

[0099]

number

[0100] (Step S620) The parameter adjustment unit 112 changes the nip width of the fixing unit 136 during image formation from W0 to W1. This change is made by the control unit 11 operating the fixing shaft distance adjustment mechanism 16. This ends the processing in FIG. 16, and the process returns to FIG. 9, where the processing from step S09 onwards is performed (return).

[0101] (Step S09) Here, the image forming unit 13 forms an image on a sheet 90 .

[0102] (Step S10) If all printing of the print job has not been completed (NO), the control unit 11 returns the process to step S07 and repeats the following process (circled number 20). On the other hand, if all printing has been completed (YES), the control unit 11 ends the process of FIG. 9 (END).

[0103] Thus, the image forming apparatus according to this embodiment comprises a fixing unit that fixes the toner image on the paper, a gloss setting unit that sets the target gloss, and a parameter adjustment unit that uses the gloss control temperature to adjust at least one of the parameters of the fixing target temperature and the paper transport conditions in the fixing unit so as to achieve the set target gloss. This allows the desired gloss to be maintained by appropriately adjusting the parameters.

[0104] (Variation 1) FIG. 17 is a flowchart showing the process performed when the paper type is changed in one print job in the first modification.

[0105] (Step S71) If the paper type has been changed during execution of the print job in step S10 (NO) (YES), the process proceeds to step S03 (circled number 10) in FIG. 9, and the process from step S03 onward is performed to obtain the paper type information. On the other hand, if the paper type has not been changed (NO), the process from step S07 (circled number 20) onward is performed. In this way, if the paper type is changed during the print job, the control unit 11 determines a new glossiness control constant xc in accordance with the paper type information. The control unit 11 then adjusts the parameters to maintain the glossiness using this glossiness control constant xc. Note that, if a common target glossiness has been set for the print job, as in the setting in area a2 of the setting screen 151, the common target glossiness is used before and after the paper type change.

[0106] (Variation 2) FIG. 18 is a flowchart showing the processing performed when a parameter adjustment is requested by the user in the second modification.

[0107] (Step S81) If the user issues an adjustment instruction other than glossiness via the operation panel 15 or the like and the parameters are adjusted (YES), the process proceeds to step S07 (circled number 20) in FIG. 9, and the following processes are performed. In this case, the parameters set by the user's adjustment are fixed, and adjustments are made to other parameters. For example, if the nip width is adjusted by the user's adjustment instruction, in step S08, adjustments are made to parameters other than the nip width, such as the fixing target temperature or the conveying speed. In this way, even if the user issues an adjustment instruction other than glossiness adjustment, the glossiness can be maintained by adjusting the parameters.

[0108] The configuration of the image forming apparatus 1000 described above is a main configuration for explaining the features of the above embodiment, but is not limited to the above configuration and can be variously modified within the scope of the claims. Furthermore, configurations provided in general image forming apparatuses are not excluded.

[0109] 1, the image forming apparatus 1000 is shown connected to the optional paper feed unit 20, but this is not limiting. The image forming apparatus 1000 may be a standalone apparatus without these options, or may be connected to another post-processing device that performs post-processing on paper on which an image has been formed by the image forming apparatus main body 10.

[0110] Furthermore, in the processes of steps S07 and S08, the fixing temperature T0 is used, but instead, the target fixing temperature Tt may be used. In step S07, the target fixing temperature Tt is acquired, and in the calculation of the adjusted parameters in step S08 (S510, S610), the current target fixing temperature Tt is used instead of the fixing temperature T0. As a result, in step S510, the next (adjusted) target fixing temperature T1 is calculated. Furthermore, if the difference between the fixing temperature and the target fixing temperature is small, the target fixing temperature may be used.

[0111] While embodiments of the present invention have been described and illustrated in detail, the disclosed embodiments are made for purposes of illustration and example only and are not intended to be limiting, and the scope of the present invention should be construed by the language of the appended claims. [Explanation of symbols]

[0112] 1000 Image forming device 10 Image forming apparatus main body 11 Control section 111 Glossiness setting section 112 Parameter Adjustment Section 12 Storage section 13 Image forming unit 136 Fixing section 14 Paper transport section 15 Operation panel 16 Fixing axis adjustment mechanism 17 Communications Department 18 Paper detection device 20 Paper feed unit 24 Paper feed transport section

Claims

1. a fixing unit that fixes the toner image on the paper; a gloss setting unit that sets a target gloss; a parameter adjusting unit that adjusts at least one parameter of a fixing target temperature and a paper transport condition in the fixing unit using the gloss control temperature so as to achieve the set target gloss; An image forming apparatus comprising:

2. 2. The image forming apparatus according to claim 1, wherein the parameter adjustment unit adjusts the parameter in accordance with a difference between the detected fixing temperature of the fixing member of the fixing unit and the gloss control temperature.

3. 2. The image forming apparatus according to claim 1, wherein the parameter adjustment unit adjusts the parameter in accordance with a difference between a current fixing target temperature for controlling a temperature of a fixing member of the fixing unit and the gloss control temperature.

4. The image forming apparatus according to claim 1 , wherein the transport conditions include parameters of a paper transport speed and a nip width in the fixing unit.

5. The image forming apparatus according to claim 1 , wherein the gloss control temperature is set in advance for each type of paper.

6. A glossiness estimation model showing the relationship between the glossiness and the glossiness control constant is provided, the adjustment of the parameters is performed using the glossiness estimation model; 2. The image forming apparatus according to claim 1, wherein the gloss level control constant is defined by the following formula: X=W / V×(T-Tgc) (In the formula, X is a gloss control constant, T is a fixing target temperature, V is a conveying speed, W is a nip width, and Tgc is a gloss control temperature.)

7. The image forming apparatus according to claim 6 , wherein the gloss level estimation model is a sigmoid function.

8. The image forming apparatus according to claim 6 , wherein the gloss level estimation model is set for each type of paper.

9. 1. A parameter adjustment method for an image forming apparatus having a fixing unit that fixes a toner image on a sheet, comprising: Step (a) of setting a target gloss level; and (b) adjusting at least one parameter of the fixing target temperature and the paper transport conditions in the fixing section using the gloss control temperature so as to achieve the target gloss level set in step (a).

10. 10. The parameter adjusting method according to claim 9, wherein in the step (b), the parameter is adjusted in accordance with a difference between the detected fixing temperature of the fixing member of the fixing unit and the gloss control temperature.

11. The parameter adjusting method according to claim 9 , wherein the gloss control temperature is set for each paper type.

12. A glossiness estimation model showing the relationship between the glossiness and the glossiness control constant is provided, The step (b) is performed using the gloss estimation model, The parameter adjusting method according to claim 9 , wherein the glossiness control constant is defined by the following formula: X=W / V×(T-Tgc) (In the formula, X is a gloss control constant, T is a fixing target temperature, V is a conveying speed, W is a nip width, and Tgc is a gloss control temperature.)

13. A control program for causing a computer to execute the parameter adjustment method according to any one of claims 9 to 12.

Images